We have been studying tumor cell motility as a component of the process of metastatic dissemination. The autocrine motility factor (AMF) is synthesized by human melanoma cells and is known to stimulate both directed and random motility in these same cells. AMF has been purified to homogeneity and appears to have a precursor (130 kDa) as well as the previously described 60-65 kDa active component (picomolar activity). The N-terminal sequence of the 60-65 kDa protein has been confirmed with 3 different protein preparations. Oligonucleotides have been synthesized which correspond to the N-terminal amino acid sequence and have been used to screen cDNA libraries made from the same melanoma cell line. In parallel studies, we have looked at the effect of pharmacologic agents which react with components of the cytoskeleton. These agents all inhibit AMF-stimulated motility but have variable effects on cellular adhesion. In a collaborative study, we have looked at a 33 kDa fragment of fibronectin and found this fragment to have the capacity to stimulate full chemotactic and haptotactic responses compared to whole fibronectin.